Influence of biofertilizers containing mycorrhizal fungi on spinach (Spinacia oleracea L.) plants grown under different light spectrums.

Mycorrhizas have a relevant role in improving crop productivity by producing growth regulators, regulating plant nutritional and hormonal balance, and solubilising nutrients in the soil. These interactions may be vital for sustainable agriculture because they mainly depend on biological processes rather than on agrochemicals to maintain plant growth. Different light quality regimes may affect the formation of mycorrhizas in soils, and in turn, the plant growth and physiology. This study aimed to assess if the plant growth at two different light treatments affects the plant-fungi interaction. The effects of biofertilizers containing mycorrhizal fungi were evaluated on Spinacia oleracea L. plants by monitoring plant growth and photosynthetic metabolism. At this purpose, not-inoculated (NI) and inoculated (I) spinach seeds with a mix of fungi and rhizobacteria were germinated in growth chamber and exposed to two different light quality treatments of 350 umol photons m-2 s-1: white light (WL) and Red-Blue (RB, 60% Red - 40% Blue) light. Inoculation with fungi induced, under WL, a lower shoot/root ratio in I compared to NI plants. Under RB, the shoot/root ratio was higher in I than in NI plants, likely due to the effect of red-blue light on root development. Irrespective of the light treatment, inoculation with mycorrhizas determined higher photosynthetic and transpiration rates and smaller synthesis of bioactive compounds such total polyphenols and anthocyanins compared to non-inoculated plants. This effect may be the consequence of improved soil-plant relations in terms of nutrients and water. These results highlight the influence of light quality on plant-fungi interaction.